Polarized type of coded track circuits



A. L. JEROME 2,520,841

POLARIZED TYPE OF CODED TRACK CIRCUITS 2 Sheets-Sheet 1 Aug. 29, 1950 Filed Aug. 28, 1946 m W L l ENTOR HIS ATTORNEY Aug. 29, 1950 A. L. JEROME 2,520,841

POLARIZED TYPE OF CODED TRACK CIRCUITS Filed Aug. 28, 1946 2 Sheets-Sheet 2 win:

(Qkwezzzin F6 2.

l -ENTOR Hi5 ATTORNEY Patented Aug. 29, 1950 POLARIZED TYPE OF CODED TRACK CIRCUITS Arthur L. Jerome, Edgewood, Pa., assign'or' to The Union Switch & Signal Company, Swissvale, Pa, a corporation of Pennsylvania Application August 28, 1946, Serial No. 693,495

3 Claims.

My invention relates to railway signaling systems of the coded track circuit class, and it has special reference to the polarized type of coded track circuits and is an improvement on the arrangements shown in Letters Patent of the United States No. 2,286,002, granted June 9, 1942, to Frank H. Nicholson.

It is an object of my invention to provide an improved system of the type described which is arranged so that energy stored in the track circuit cannot produce improper operation of the relays employed in the system.

Another object of my invention is to provide an improved system of the type described which is arranged so that the detector relay employed therein cannot be improperly energized from the track batteries in the event the coding device contacts which control the circuits of the detector relay winding and of the track batteries fail to interrupt one of these circuits before establishing the other circuit.

Another object of my invention is to provide an improved system of the type described which is arranged in such manner that the track relays employed therein cannot be improperly energized from the impulse or feed-back batteries in the event the impulse relay contacts which control the circuits of the track relays and of the batteries fail to interrupt one of these circuits before establishing the other.

Other objects of my invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings.

In practicing my invention, I provide a coded track circuit system employing a master code, which may be of one polarity or the other depending on traffic conditions in advance, which master code is transmittedfrom the first end of a track section to the second end of the track section. I also provide means for generating a feed-back code, of the same polarity as the master code, which is transmitted from the second end of the track section to the first end of the track section and arranged so that there is no danger of either the track relay at the second end of the track section or the detector relay at the first end of the section becoming energized by energy stored in the track circuit or as a result of overlapping contacts on the code generating apparatus.

I shall describe one embodiment of my invention together with two modifications thereof which I may employ and shall then point out the novel features thereof in claims.

In the drawings, Fig. 1 is a diagram of a section of railway track equipped with apparatus embodying my invention, and Figs. 2 and 3 are diagrams showing modified forms of apparatus which may be employed at the exit end of the track section.

In the drawings, similar reference characters refer to similar parts in each of the three views.

Referring to Fig. l of the drawings, there is shown. therein a section of railway track having track rails I and 2 over which traffic normally moves in the direction indicated by the arrow, that is from left to right. The track rails of each section are separated from the rails of the adjoining sections by insulated joints 3 in the usual manner. A signal S, which is here shown as a conventional three-aspect color-light type, having a green, yellow, and red lamp, governs traffic entering the track section in the normal direction.

The track section has at the entrance or second end thereof a normal track relay NPR and a reverse track relay RTR each having a winding receiving energy over the section rails. These relays are of a type the contacts of which are biased to a released position and become picked up on the supply of energy of one polarityonly to the relay winding, while these relays are connected with the track rails in such manner that they respond to energy of opposite polarity supplied over the track rails. The normal track relay has associated with it a decoding transformer NDT, a rectifier NRX and a normal code detection relay NH, and the reverse track relay has associated with it a decoding transformer RD'I', a rectifier RRX and a reverse code de tection relay RH. The equipment at the entrance end of the block also includes an impulse relay IR and the batteries NFB and RFB from which impulses of feed-back energy are supplied to the rails of the track section, and an auxiliary relay HP which is governed jointly by relays NH and RH.

The equipment at the exit or first end of the track section includes a detector relay KR, normal track battery NTB, reverse track battery R'I'B, a coding device CR, an approach relay AR, and a decoding transformer KT. The equipment at the right-hand or first end of the section also includes a relay PC which may be governed in any appropriate manner, as by traific conditions in advance, so as to be picked up at times and to be released at other times.

The detector relay KR is of the polarized type and has movable contacts which are shifted to their left-hand or normal position when the relay winding is supplied with energy which flows through the winding from the left-hand terminal to the righth-and terminal, while these contacts are shifted to their reverse or right-hand position when the relay winding is supplied with energy which flows through the winding from the right-hand terminal to the left-hand terminal. In addition, the relay KR is of a type the contacts of which when moved to either position will remain in that position until the relay winding is energized with current of the polarity effective to move the relay contacts to their other position.

The coding device GR is provided with contacts which are recurrently picked up and released at a certain rate.

The approach relay AR may be employed to 1 control circuits for energizing the lamps of the signal, not shown, for the adjacent. section in appropriate purpose.

The equipment is shown in the condition which advance, or to control circuits for any other it assumes when the track section is vacant and tramc conditions in advance are suchthat the relay PC is energized, causing master code of normal polarity to be supplied to the rails. When contact it of coding device OR is in its picked-up position, as shown in the drawings, the normal.

track battery NTBis connected across the rails I and 2 by a circuit which includes in series therewith front contact 8 of relay PC, limiting resistor Ra, front contact III of coding device CR, and

winding of relay KR. As hereinafter explained,

the contacts of the normal code detection relay NH'are picked up and the contacts of the reverse code detection relay RH and the contacts of impulse relay IR are released at this time Accordingly energy flows from the normal track battery NTB through a circuit which is traced from the positive terminal of the battery NTB over front I contact 8 of relay PC, through resistor Ra, front I contact III of coding device CR, through the winding of relay KR from right to left, track rail I,

- NTR, while it is also such that the contacts of the detector relay KR are shifted to their right-hand or reverse position as shown.

On picking up of contact I5 of relay NTR. a connection is established from terminal B of a local source of direct current, not shown, to one terminal of the primary winding of the decoding,

transformer NDT. The center terminal of this winding is connected to terminal C of the source so that one-half of the transformer primary winding is energized and an impulse of energy is induced in each of the transformer secondary windings.

The energy impulse induced in the transformer secondary I6 is rectified by rectifier NRX and supplied to the winding of relay NH, while the impulse of energy induced in the other transformer secondary winding I! is supplied to the impulse relay IR over a circuit including front contact I9 of relay NH. However, the relay IR is of a type the contacts of which become picked up only when energy of one polarity is supplied to the relay winding and the various parts of the equipment are arranged so that the energy supplied to the relay IR on movement of the track relay contacts to their picked-up positions is of such polarity as to be ineffective to pick up the contacts of relay IR.

Similarly, on movementof contact 2i of relay KR to its right-hand position a circuit is established to energize one portion of the primary winding of transformer KT from a local source of direct current, not shown, while contact 22 of the relay KR rectifies the energy supplied from the secondary winding of transformer KT to the approach relay AR.

After a brief time interval the contact ID of coding device CR moves to its released position. thereby interrupting the supply of energy from the track battery NTB over the circuit previously traced, while contact I9 connects the winding of relay KR across the track rails I and 2. On this interruption in the supply of energy from the battery NTB, the contacts of track relay NTR release and contact 15 establishes a circuit to energize the other portion of the primary winding of transformer NDT. As a result, an impulse of energy is induced in each of the transformer secondary windings. These impulses are of the polarity opposite to that of the impulses present on movement of the track relay contact to its pickedup position, and the energy supplied to the relay IR is effective to pick up the contacts of this relay momentarily. I

On picking up of the contacts of relay IR contact I l interrupts the circuit traced above for connecting the winding of the track relay NTR across the track rails and establishes a circuit to supply energy from the battery NFB to the relay KR o'ver track rails I and 2. This circuit is traced from the positive terminal of the battery NFB, through resistor Rb, over front con-tact I4 of relay IR, front contact ii! of relay NH, back contact i I of relay RH, winding of relay N'IR from right to left, track rail I, winding of relay KR from left to right, back contact II] of coding device CR, and track rail 2 to the negative terminal of battery NFB. At this time therefore, the relay KR is energized by current supplied from the battery NFB. The direction of flow of this energy through the winding of relay KR is opposite to that of the energy supplied to the relay KR from the battery 'NTB, and accordingly the contacts'of the relay KR are shifted to their left-hand or normal position so that contact 2| establishes a circuit to energize the other portion of the primary winding of transformer KT, while contact 22 establishes a circuit to supply energy from the left-hand portion of the transformer secondary winding to the approach relay AR.

In addition, as long as the relay IR is picked up the track relay NTR is energized by current supplied from the battery NFB. However, the direction of flow of energy through the relay winding is such that the energy is ineffective to pick up the relay contacts, but rather serves to maintain these contacts in their released position.

After a brief time interval, the contacts of relay IR release and interrupt the supply of energy from the battery NFB to the section rails, while contact I4 reconnects the track relay NTR across the section rails. On this interruption of the supply of energy from the battery NFB energy ceases to be applied to the relay KR, but because of the characteristics of the relay its contacts remain in the position to which they have just been moved,

Subsequently the contact ll! of coding device CR picks up and interrupts the circuit connecting the relay KR across thesection rails and again establishes the circuit for supplying energy from the battery NTB to the relays KR and NTR in series.

As long as the track section is vacant and relay PC remains picked up, the equipment continues to function in this manner. The contacts of the normal track relay NTR pick up on the supply of impulses of normal master code energy, while these impulses effect movement of the contacts of the detector relay KR to their right-hand or reverse position. During the off intervals between the impulses of the normal master code the track relay contacts release, and the impulse relay IR contacts pick up momentarily and disconnect the track relay from the track rails and establish the circuit to supply an impulse of feedback energy from the battery NF'B to the relay KR. These impulses of feed-back energy effect movement of the contacts of relay KR to their normal or left-hand positions. As a result of picking up and releasing of the track relay contacts, energy is supplied through the transformer NDT to the relay NH, while as a result of movement of the contacts of the detector relay KR between their normal and reverse positions, energy is supplied through the transformer KT to the relay AR. The relays AR and NH and RH are of a type which are somewhat slow in releasing so that their contacts remain picked up during the intervals between the supply of impulses of energy thereto. Therefore, as long as the track section is vacant, and relay PC remains picked up, the relays NH and AR are picked up. Auxiliary relay HP is energized at this time by a circuit which may be traced from terminal B, over front contact 25 of relay NH, and through the winding of relay HP to terminal C. Relay HP in cooperation with relay NI-I controls the supply of energy to the lamps of signal S at the entrance to the track section, which is here shown as a color-light type of signal. At this time, energy is supplied to the green lamp G of signal s by a circuit which is traced from terminal B over front contact 26 of relay HP, front contact 21 of relay NH, and through the filament of the lamp to terminal C. Therefore, with the track section vacant, and relay PC picked up, signal Sdisplays a green aspect, and approach relay AR is picked up.

When a train moving in the normal direction of traffic, that is from left to right, enters the track section, that is from left to right, enters the track section, the wheels and axles of the vehicles of the train shunt the track relay NTR so that its contacts thereafter remain released. Accordingly, impulses of energy are not supplied through the transformer NDT to the impulse relay IR and the contacts of relay IR remain released and do not supply impulses of feed-back energy to the section rails and to the relay KR. In addition, energy is not supplied through the transformer NDT to the relay NH and the contacts of relay NH release, interrupting the previously traced circuit for relay HP and for the green lamp G of signal S, and after relay HP releases, a circuit is established over its back contact 26 to supply energy to the red lamp R. of signal S.

At this time the coding device CR continues to operate and to supply impulses of normal master code energy to the section rails. These impulses of energy cause the contacts of relay KR to move to their reverse position. However, at this time, as impulses of feed-back energy are not supplied to the relay KR, the contacts of this relay remain in their reverse position and energy is no longer supplied from transformer KT to the approach relay AR. Accordingly, the contacts of relay AR release and interrupt or establish the approach control circuits.

When the train advances far enough to vacate the section, master code energy again flows from the exit end of the section to the entrance end of the section. However, due to the train in the next track section, relay PC, which may be controlled in a manner similar to that previously explained for relay HP, is released and the reverse track battery RTB now supplies energy to the track rails. At this time when contact H] of coding device CR is picked up, normal track relay NTR and reverse track relay RTR are energized in series by a circuit which is traced from the positive terminal of battery RTB over track rail 2, through the winding of reverse track relay RTR, back contact I2 of relay NI-I, back contact ll of relay RH, through the winding of normal track relay NTR, track rail I, through the winding of relay KR from left to right, front contact ll] of coding device CR, resistor Ra, and back contact 8 of relay PC to the, negative terminal of battery RTB. The polarity of the impulse of master code energy supplied from battery RTB is such that the direction of flow of energy through the winding of normal track relay NTR is opposite to that which is effective to pick up the contacts of this relay, while the direction of flow of energy through the winding of reverse track relay RTR is such that it is effective to pick up the contacts of this relay. Accordingly, contact 29 of relay RTR picks up and establishes a circuit to supply energy to the upper portion of the primary winding of transformer EDT, and interrupts the circuit for supplying energy to the lower portion of this winding. As a result, energy is supplied to the relay RH through transformer RDT and rectifier RRX, and relay RH picks up, and its contact H interrupts the circuit traced above for connecting track relays RTR and NTR across the track rails in series andestablishes a circuit to connect relay RTR across the track rails independently of relay NTR. This circuit is traced from rail 2 through the winding of relay RTR, over back contact l2 of relay NH, front contact H of relay RH, and back contact 30 of relay IR to track rail I. In addition, when relay RH picks up, a circuit is established for relay IR which is traced from one terminal of the secondary winding 33 of the transformer RDT,

- over front contact 3! of relay RH, through the winding of relay IR and returning to the other terminal of the secondary winding 33. The apparatus is arranged so that only the impulse of energy induced in the transformer secondary winding 33 when relay RTR releases is effective to cause the contacts of relay IR to pick up.

Also, at this time, the flow of current through relay KR is such that the contacts of this relay operate to their left-hand or normal position, and as a result an impulse of energy is supplied to relay AR through decoding transformer KT. After a brief time interval, the contact I!) of coding device CR moves to its released position, thereby interrupting the supply of energy from the reverse track battery RTB traced above, while contact I ll connects the winding of the relay KR across the track rails I and 2. On this interruption in the supply of energy from the battery RTB the contacts of reverse track relay RTR release and contact 29 establishes a circuit to energize the lower portion of theprimary winding 'of transformer RDT. As a result, an impulse of energy is induced in each of 'the transformer secondary windings, and, as explained above, the energy supplied to the relay IR from the secondary winding 33 on release of relay'RTR is effective to pick up the contacts of this relay.

When the contacts of relay IR pick up contact 39 interrupts the circuit traced above for connecting the winding of relay RTR across the track rails and establishes a circuit to supply energy from the battery RFB to the relay KR over the rails I and 2. This circuit is traced from the positive terminal of battery RFB, through resistor R0, over front contact of relay IR, front contact I I of relay RH, back contact I2 of relay NH, through the winding of relay RTR, track rail 2, back contact Id of coding device CR, through the winding of relay KR from right to left, and through track rail l to the negative terminal of battery RFB. At this time, therefore, the relay KR is energized by current supplied from the battery RFB. The direction of flow of this energy is opposite to that of the energy supplied to the relay KR from the reverse track battery RTB and accordingly the contacts of relay KR are shifted to their right-hand or reverse positions so that contact 2i establishes a circuit to energize the right-hand portion of the primary winding of the transformer KT, while contact 22 establishes a'circuit to supply energy from the transformer secondary winding to the approach relay AR.

In addition, reverse track relay RTR is energized by current supplied from the battery RFB. However, the direction of flow of energy through the relay winding is such that the energy is ineffective to pick up the relay contacts, but on the contrary serves to hold these contacts more firmly in their released positions.

After a brief time interval, the contacts of relay IR release and interrupt the supply of energy from the battery RFB to the track rails, while contact as reconnects the reverse track relay RTR across the track rails. On this interruption of the supply of energy from the battery RFB energy ceases to be supplied to the relay KR, but, as previously explained, the relay operating characteristics are such that the relay contacts remain in the position to which they have just been moved.

Subsequently, the contact III of coding device CR picks up and interrupts the circuit connecting the relay KR across the section rails and again establishes the circuit for supplying energy from the battery RTB to the relays KB. and RTR in series.

The equipment continues to function in this manner, as long as the track section is vacant, and the contacts of relay PC are released. The reverse track relay contacts pick up on the supply of impulses of reverse master code energy, while these impulses effect movement of the contacts of the detector relay KR to their left-hand or normal positions. During the off intervals between the impulses of reverse master code energy, the reverse track relay contacts release, while the impulse relay IR contacts pick up momentarily and disconnect the track relay from the track rails and establish the circuit to supply an impulse of feed-back energy from the battery RFB to the relay KR. These impulses of feedback energy effect movement of the contacts of relay KR to their right-hand of reverse posi- 8 tions. As a'result of operation of the reverse track relay RTR, energy is supplied through the transformer RDT .and rectifier RRX to the relay RH, while as a result of movement of the contacts of the detector relay KR between their normal and reverse positions, energy is supplied through the transformer KT to the relay AR. The relay RH is of a type which is somewhat slow in releasing similar to relays NH and AR, so that its contacts remain picked up during the intervals between the supply of impulses of energy thereto. At this time, relay HP is energized by a circuit which is traced from terminal B, over front contact 35 of relay RH, and through the winding of relay HP to terminal 0. Accordingly, contact 26 of relay HP is picked up, interrupting the supply of energy to the red lamp R of signal S, and establishing a circuit including the back contact 21 of relay NH for the yellow lamp Y of signal S. Therefore, with the track section vacant, and relay PC released, the signal S displays a yellow aspect, and approach relay AR is picked up.

When trafiic conditions are such that relay PC becomes energized, its contact 3 picks up, interrupting the circuit of the reverse track battery RTB, and establishing the circuit of the normal battery NTB. The impulses of energy supplied at this time from battery NTB to reverse track relay RTR are of opposite polarity from that required to pick up the relay, and accordingly, relay R'IR releases and remains released. After a short time interval relay RH releases, since energy is no longer supplied to it from the decoding transformer RDT. Back contact I! of relay RH now establishes a circuit connecting relays NTR and RTR in series across the track rails I and 2. This circuit is traced from track rail I, through the winding of relay NTR, over back contact II of relay RH, back contact I2 of relay NH, and through the winding of relay RTR to track rail 2. As previously explained, the impulses of normal master code energy which are being received at the entrance end of the block at this time are of such polarity as to be ineffective to pick up reverse track relay RTR, but are effective to pick up normal track relay NTR. Therefore, relay NTR, picks up and releases in accordance with the impulses of normal master code energy received at this time.

,Relay NH now receives energy from the decoding transformer NDT through rectifier NRX and its contacts pick up, with the result that contact l2 interrupts the circuit traced above by which relays NTR and RTR were connected in series across the track rails I and 2, and establishes a circuit for connecting relay NTR across track rails I and 2 independently of relay RTR. This circuit is traced from track rail I through the winding of relay NTR, over back contact I! of relay RH, front contact I2 of relay NH, and back contact I4 of relay IR to section rail 2. In addition, when relay NH picks up, its front contact I9 reconnects the winding of impulse relay IR to the secondary winding ll of transformer NDT, the winding of relay IR having been previously disconnected from secondary winding 33 of transformer RDT by the release of contact 3| of relay RH.

Accordingly, each time relay NTR releases, relay IR will pick up momentarily, and its front contact I4 will connectbattery NFB to the track rails I and 2 as has been previously explained.

Relay HP is so selected that its release time is longer than the time interval between the release of one of the relays or RH and the picking up of the other of these relays. "a result, when relay RH releases, the circuit 'pre' viously traced over front contact 35 of relay RI-l is opened, but relay HP maintains its contacts in their picked up position, and subsequently is re-energized by front contact'2'5 of relay NH.

Accordingly, on a transfer of'the master code from one polarity to the other polarityj the relay HP will remain picked up, and thecircuit for supplying energy'to the red lamp R will not be established. Consequently, there will be no flash of the red lamp'wh'ile the code detecting equip ment is transferring from one polarity to the other polarity. 4

In like manner the relay AR may be slow enough'in releasing to remain picked .up in the intervalin" which the supply of energy thereto is interrupted because 'of the change in the polarity of the master code energy supplied over the section rails.

' At this'tirne, when relay NH picks up, energy is suppliedto the green lamp G of signal 5', over a circuit including iront contact 28 of relay HP, and front contact 2'! of relay NH, while the supply of energy to the yellow lamp Y is interrupted by contact 27 of'relay NH. The equipment is now restored to its normal condition, as shown in the drawing and previously described.

On a change in the position or the contact of relay PC, with a resultant change in the polarity of the master code energy supplied through the relay KR to the track rails, the contacts of the relay KR maybe moved from one position to the other, thereby causing an impulse of energy to be supplied through the decoding transformer KT to relay AR. However, only one movement of the contacts of relay KR can result from this change in the polarity of the energy supplied to the track rails, and only one impulse of energy will be supplied to relay AR. ihe relay AR is of a type the contacts of which are slow to pick up,and the relay is selected so that its contacts, if released, will not pick up in response to a single impulse of energy supplied from the trans= former Accordingly, if while the section is occupied, the relay PC changes the polarity of the master code supplied to the section rails, the relay AR will not pick up but will'remain released.

This system is arranged so that the polarity of the master code energy and feed-back energy is such that there is no'possibility of improper operation of the detector relay by energy stored in the track circuit when the track circuit is occupied.

Whencontact IU of the coding device CR moves out of engagement with its front contact, the supply of energy to the track rails from battery NTBor RTB is interrupted, but because of the inductance of the track rails, which at this time are connected by the wheels and axles of a train occupying the section, and the conductance of the track ballast toward the exit end of the track circuit, energy continues to flow in this circuit for a period of time so that under most ballast conditions, when the contact it; engages its back contact, energy stored in the track circuit will flow 'for a short period of time through the Wind'- ing of relay KR. The direction of flow of this energy is the same as that previously supplied to the track circuit from battery NTB orRTB so that the only efiect of the flow of stored energy is to maintain the detector relay contactsin the position to which theyhave already-been moved bythe energysupplied from battery NIBprQRTB. Aceordingly,.no change in energiz'ation of the primary winding or transformer KT occurs and energy will not be" supplied to 'therelaTAR.

',This circuit" is" also arranged so"that,"if the the p ne de ic clta ji rr t y ad sted or buildup arid the movable contact. Ill f es' its front and back contact at the same i e. impr peroper i npr the relay KR cann q uvf Referring to the drawings, it will be seen that if the 'front and back contacts of'coding' 'deyi'ce CB. oyerlfap, the battery NTB or batteryRTB will beshort'circuited through resistor Rd, while'ho cir uit 'be' established to" improperly ener giz relay "5?;imilarly, the circuit provided by my inventioiiis arranged that, if contact lfl or contact 3?? "of relay 'IRSl'lbuldbe incorrectl adjusted or should build up so that it engages its frontand back cofitact at thesa'nhe timefits' associated trackrelay cannotbe energizedby the associated battery 'NFB 'orbat'tery RFIBI If contact i i of relay IR should overlap," battery NFB' would be short-:dircu'ite'd' through res1 or R5 and if contact 3d of relay should o erlap, ba tery RFB would be snort-enemies through resistor'Rc'.

- Additionally, if contact If; 6r contact'tii' should 'k' or fuse in its picked-up position, the apus is so anat ema-t improper operation lo t result, since ,the'polarity of the energy siipplied dam the batteriesNFB'and RFB is's'uch that the now of feed-backfenergy through the associated track relays is always in the'direction opposite 'to that'requirediorfthe pick up of the rna s; Energy from battery is supplied to the section rails o ers cir uit including'a front conta t' of the normal code detecting relay and a back contactof the reverse code'de'tecting relay arise that if {front Co t ct [4 "of relay IR should remain closed 'ene'rgy'iro'm battery NFB wilLbe supplied through the winding 61; relay NTR as longas relay :NH remains picked up. The energy 'isupplied ,fromflbattery through the winding of jrielayifi'TR forces the contacts ofrelay ii'llt t' theirreleased'position 'andholds them in that position, ,w'hilethis er:iergy prevents response qr relay NQTR to master code lener'gy'su'p pliedover the trackrails. Accordingly, relay NTR remains released and energy ceases .tobe supplied through the transformer ND'I to relay NH and its contacts release with the result that Contact l ZQinterrupts th ecircuit of battery NFB and'establishe's the circuit'for connecting relays NIH and ,RfIfR across the track rails in series. he la IB m new re i t master code en stee in rqlar t su plie bv r he t k rails and willcause energy to be suppliedthroug h transformerNDT to relay NI -Ito pick up its contacts. Whenirelay NI I picks up its contact 12 establishes the circuit for supplying energy from batteryNEB through therelay N TR whichforces thecontact of relay NTI-fR to release, and the cycle of operation previously described is repeated.

Accordingly, ,contac t {Zlof relay NH repeatedly transfers thesupply of energy from the green lamp Gof signaLS to ,the yellow lamp Y and backtothegreen lamp G. The flashing of the signal lampswill call attention to the improper operation ,of the control apparatus, but since.

smear In like manner, while master energy of reverse polarity is supplied to the exit end of the section,if front contact 30 of relay IR should stick or fuse closed, an operation of the apparatus similar to that just described would occur. However, since the relay NH is released at this time, and relay HP is sufllciently slow in releasing to bridge the releasing and picking up of relay RH, the circuit for supplying energy to the yellow lamp Y would not be interrupted.

' Improper operation of contact M of relay IR will not have an efiect on the apparatus while reverse master code energy is being received. Similarly, improper operation of contact 30 of relay IR will not have an efiect on the apparatus while normal master code energy is being received.

The entrance end equipment provided by this invention is arranged so that energy stored in the track circuit cannot cause undesired operation of the track relays.

If a train backs into a section, or if a section includes a switch at an intermediate point and a train enters the section through the switch, the

contacts of whichever one of the track relays NTR or RTR which is then picked up will release and energywill be supplied to the impulse relay IR so that its contacts pick up and cause an impulse of feedback energy to be supplied to the track rails from battery NFB or RFB according as relayNI-l or RH is picked up. This impulse of feed-back energy will be prevented from reaching the detector relay KR due to the presence of the train in the section; However, as the train is some distance removed from the entrance end of the tracksection the feed-back energy flows through a substantial part of the track circuit and considerable energy may be stored in the track circuit.

On subsequent release of the impulse relay contacts the supply of energy from the battery NFB or RFB is cut off while the winding of the corresponding track relay is connected across the track rails. As explained in connection'with theequipment at the exit end of the section, the energy stored in the track circuit flows in the same direction as that supplied from the battery-to the'track rails. Accordingly, the energy in the track circuit will flow throughthe track relay in the wrong direction to pick up the relay contacts. -The track relay contacts, therefore, remain released and no energy is supplied to the impulse relay so the contacts of the im-' pulse relay remain released and no more impulses of feed-back energy are supplied to section rails.

In Fig. 2 of the drawings there is shown in fragmentary diagram of a modified form of apparatus which I may employ at the right-hand or exit end of the section. This equipment is similar to that shown in Fig. 1, but difiers therefrom in that the contact 2| of detector relay KR and a contact 9 of relay PC directly control the supply of energy to the approach relay AR.

In this modification the circuit of relay AR is arranged so that it is complete when contact 2| of detector relay KR is in the position to which it is moved by the impulses of feed-back energy. The polarity of the feed-back energy supplied to the detector relay KR is governed by the polarity of the master code energy, and the polarity of the master code is governed by the relay PC.

Accordingly, a contact of relay PC is used to determine which position of contact'2l of relay KR is the position to which the contact 2| will be.

Y 9 of relay PC.

. l2 operated by the impulses of feedback energy. With the relay PC picked up, the direction of flow of impulses of master code energy through the winding of relay KR is such that contact 2| of relay KR is operated to its right-hand or reverse position, and back contact 9 of relay PC is open, with the result that energy is not supplied to the winding of relay AR. However, the impulses of feed-back energy at this time flow through the winding of relay KR in the direction to operate its contact 2| to its left-hand or normal position, and relay AR is then energized over the circuit including the normal contact 2| of relay AR and. front contact 9 of relay PC.

When a train enters the section at this time the supply of impulses of feed-back energy to the detector relay KR is cut chi, and the relay contact 2| is moved to its right-hand or reverse position by the impulses of normal master code energy to thereby cut off the supply of energy to the approach relay AR. As the detector relay contact 2| remains in its reverse position the approach relay is deenergized and its contacts release.

When the contacts of relay PC are released, impulses of reverse master code energy flow through the relay KR in such a direction as to operate its contacts to their left-hand or normal position, while the impulses of feed-back energy flow through the relay in such a direction as to move its contacts to their right-hand or reverse position. Accordingly, impulses of energy will be supplied to the relay AR by a circuit including reverse contact 2| of relay KR and back contact If a train enters the section at this time the supply of feed-back energy to the detector relay is cut on", and the relay contact is moved to its left-hand or normal position by the impulses of reverse master code energy to thereby cut off the supply of energy to the approach relay AR. As the detector relay contact remains in its normal position the approach relay is deenergized and its contacts release.

The modification shown in Fig. 3 employs a detector relay KRA which is similar to the track relays and is of a type the contacts of which when released become picked up only when energy flows in one direction through the relay winding, and which when picked up become released on interruption of the supply of energy to the relay Winding or on the supply of energy of the opposite polarity to the relay winding.

The exit end equipment shown in Fig. 3 is intended to be used with entrance end equipment of the type shown in Fig. 1, while it is contemplated that the positive terminal of battery NFB associated with the entrance end equipment will be connected to the same track rail as the positive terminal of the track battery TB is connect-- ed when the contacts of relay PC are picked up. In operation when the contacts of coding device CR are picked up, contact it establishes a circuit to supply an impulse of master code energy from the battery TB to the section rails through the winding of the detector relay KRA and pole changing contacts 38 and 39 of relay PC. The direction of flow of energy in this circuit is such that the energy is ineflective to pick up the contacts of the detector relay, but instead tends to maintain them more firmly in their release position.

When contact ID of coding device OR is picked up and the contacts 38 and 39 of relay PC are picked up the positive terminal of the battery TB is connected through the. winding OfrelayKRA.

and over front contact 38 of relay PC to track rail I while the negative terminal of the battery is connected over front contact 39 of relay PC to track rail 2. Accordingly, with equipment at the left-hand end of the section arranged as shown in Fig. 1, energy supplied to the track rails when relay PC is picked up will operate relay NTR to pick up relay NH while relay IR operates on release of relay NTR to connect battery NFB across the track rails with the positive terminal of the battery connected to track rail I. The energy supplied from battery NFB to the track rails flows from rail I over front contact 38 of relay PC through the winding of relay KRA from left to right, over back contact it of coding device CR, and front contact 3'9 of relay PC to rail 2. The direction of how of energy through the winding of relay KRA, therefore is such as to be effective to operate the relay and contacts are picked up by this energy.

In like manner, when contact In of coding device OR is picked up and the contacts 38 and 39 of relay PC are released the positive terminal of the battery TB is connected through the winding of relay KRA and over back contact 39 of relay PC to track rail 2 while the negative terminal of the battery is connected over back contact 38 of relay PC to track rail I. Accordingly, the energy supplied to the track rails when relay PC is released will operate relay RTR to pick up relay RH while relay IR operates on release of relay RTR to connect battery RFB across the track rails with the positive terminal of the battery connected to track rail 2. The energy supplied from 'battery RFB to the track rails fiows 'from track rail 2 over aback contact 39 of relay PC, through the winding of relay KRA from left to right, over back contact ll] of coding device CR and back contact 38 of relay PC to rail I, The direction of flow of feed-back energy effective to operate the relay and its contacts are picked up by this energy.

If desired the winding of relay KRA may be short-circuited or shunted by the circuit governed by front contact 42 of relay CR to thereby reduce or eliminate the resistance of the relay winding in the circuit for supplying energy from the battery TB to the track rails as explained in the above identified patent to F. H. Nicholson.

On subsequent picking up of the contact of coding device CR, the circuit connecting relay KRA-across the track rails is interrupted and the track battery TB is again connected across the track rails in series with the winding of relay KRA, so that another impulse of master code energy is supplied to the track rails, while the contacts of relay KRA release. This arrangement is similar to that shown in Fig. l, in that the overlapping of the coding device contact III will result only in short-circuiting the track battery TB through the resistor Ra and cannot result in the supply to relay KRA of energy which will pick up the relay contacts.

As long as the track section is vacant the equipment continues to operate in this manner, that is during the picked-up periods of the coding device contacts impulses of master code energy are supplied to the section rails while the detector relay contacts release, and when the coding device contacts are released the detector relay winding is connected across the section rails so that the relay contacts are picked up by impulses of feedback energy. The contacts 40 and 4| of relay KRA may be used to control any type of code de- 14 meeting means to operate an approach relay, so that as long as the contacts of relay KRA are operated, the approach relay will be energized. and when the contacts of relay KRA remain at rest, the approach relay will not be energized.

It is to be understood that my invention is not necessarily limited to the transformer type of code detecting means shown in Figs. 1 and 2 for detecting the code following operation of relay KB and previously described, but may incorporate other code-detecting means well known to the art.

Although I have herein shown and described several forms of railway signaling systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a coded railway signaling system in combination, a section of railway track, a first and a second code following track relay located at the first end of said section and operated by coded energy supplied over the section rails, each of said track relays having a contact biased to a released position and movable therefrom to a picked up position when and only when energy flows through the relay winding in a selected direction, said track relays being connected with the section rails in such manner that the first track relay responds to energy of normal polarity and the second track relay responds to energy of reverse polarity, a first code detecting relay responsive to'code'following operation of said first track relay, a second code detecting relay responsive 'to code following operation of said second track relay, a third code following relay I 40 I 4 v i through the Winding of relay KRA is therefore loca ed at the second end of said section, said third code following relay having acontact which is movedto a first position when energy of one polarity is supplied through the relay winding and is moved to a second position when energy of theother polarity'is supplied through the relay winding, -a coding device having a contact recurrently operated between a. first position in which it connects a track battery across the section rails through the winding of said third code following relay and a second position in which it connects the third code following relay across the section rails independently of said battery, means for at times causing the energy supplied from said track battery to the section rails to be of normal polarity and at other times to be of reverse polarity, means effective when said first code detecting relay is energized for supplying to the section rails at the first end thereof through the winding of said first code following relay an impulse of energy of normal polarity in response to each movement of the contacts of said first code following relay to their released position, means effective when said second code detecting relay is energized for supplying to the section rails at the first end thereof through the winding of said second code following relay an impulse of energy of reverse polarity in response to each movement of the contacts of said second code following relay to their released position, and a control relay responsive to operation of said third code following relay by energy supplied over the section rails.

2. In a coded railway signaling system, in combination, a section of railway track, a first and a second code following track relay located at the first end of said section and operated by coded 15 energy supplied over the section rails, each of said track relays having a contact biased to a released position and movable therefrom to a picked up position when and only when energy 1 flows through the relay winding in a selected direction, said track relays being connected with the section rails in such manner that the first track relay responds to energy of normal polarity and the second track relayresponds to energy of reverse polarity, a'first code detecting relay responsive to code following operation of said first track relay, a second code detecting relay responsive to code following operation of said second track relay, a third code following relay located at the second end of said section, said third code following relay having a contact which is moved toa first position when energy of one polarityis supplied through the relay winding and is moved to a second position when energy of the other polarity is supplied through the relay winding, a coding device having a contact recurrently operated between a first position in which it connects a track battery across the section rails through the winding of said third code following relay and a second position in which it connects the third code following relay across the section rails independently of said battery, means for at times causing the energy supplied from said track battery to the section rails to be of normal polarity and at other times to be of reverse polarity, means at the first end of said section for supplying impulses of energy to the section rails in the intervals between impulses of energy supplied to the section rails at the second end thereof, means for causing the energy impulses supplied to the section rails at said first end to be of normal or of reverse polarity ac cording as said first or said second code detect- 16 when energy flows through the winding of the relay in a selected direction, a coding device having a contact recurrently operated between a first position in which it connects a first terminal of the winding of said code following relay to a first terminal of a source of energy and a second position in which it connects said first terminal of the winding of said code following relay to a second terminal of said source, the connections between said source and the winding of said code following relay being arranged so that energy from said source flows through said relay winding in the reverse of said selected direction, a control relay reversibly connecting the rails of said section to the second terminal of the winding of said code followin relay and the first terminal of said source, respectively, normal and reverse code detecting means at the second end of said section responsive to coded energy of normal and reverse polarity respectively supplied over the section rails, means ,for at times supplying impulses of energy to the section rails at the second end thereof, and means governed by at least one of said code detecting means for controllingthe polarity: of the impulses of energy supplied to the second end of the section in accordance with the condition of said control relay. r

ARTHUR L. JEROME.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,976,437 Crago Oct. 9, 1934 2,244,901 Staples June 10, 1941 2,286,002 Nicholson June 9, 1942 2,291,579 Judge July 28, 1942 2,349,680 Shields May 23, 1944 2,352,987 Wight July 4, 1944 2,354,024 Jerome July 18, 1944 2,360,948 Jerome Oct. 24, 1944 2,430,314

Van Horn Nov. 4, 1947 

